A model with private information is constructed that supports conventional arguments for a government monopoly in supplying circulating media of exchange. The model also yields predictions, including rate-of-return dominance of circulating media of exchange, that are consistent with observations from free banking regimes and fiat money regimes. In a laissez faire banking equilibrium, fiat money is not valued, and the resulting allocation is not Pareto optimal. However, if private agents are restricted from issuing circulating notes, there exists an equilibrium with valued fiat money that Pareto dominates the laissez faire equilibrium and is constrained Pareto optimal.

An overlapping generations model is developed that contains labor markets in which adverse selection problems arise. As a response to these problems, quantity rationing of labor occurs. In addition, the model is capable of generating (a) random employment and prices despite the absence of underlying uncertainty in equilibrium; (b) a statistical (nondegenerate) Phillips curve; (c) procyclical movements in productivity; (d) correlations between aggregate demand and unemployment (and output); (e) an absence of correlation between unemployment (employment) and real wages. In addition, the Phillips curve obtained typically has the "correct" slope. Finally, the model reconciles the theoretical importance and observed unimportance of intertemporal substitution effects, and explains why price level stability may be a poor policy objective.

The classical and early neoclassical economists knew that the essential function of money was its role as a medium of exchange. Recently, this idea has been formalized using search-theoretic noncooperative equilibrium models of the exchange process. The goal of this paper is to use a simple model of this class to analyze four substantive issues in monetary economics: the interaction between specialization and exchange, dual fiat currency regimes, the welfare improving role of money, and the susceptibility of monetary economies to extrinsic uncertainty.

We propose a model in which an unanticipated reduction in the money supply leads to a contemporaneous increase in inventories followed by periods with lower output. This persistent real effect does not require price-rigidity or real shocks and confusion. It is obtained in a model in which markets are cleared and agents are price-takers.

Different monetary aggregates covary very differently with short term nominal interest rates. Broad monetary aggregates like Ml and the monetary base covary positively with current and future values of short term interest rates. In contrast, the nonborrowed reserves of banks covary negatively with current and future interest rates. Observations like this 'sign switch' lie at the core of recent debates about the effects of monetary policy actions on short term interest rates. This paper develops a general equilibrium monetary business cycle model which is consistent with these facts. Our basic explanation of the 'sign switch' is that movements in nonborrowed reserves are dominated by exogenous shocks to monetary policy, while movements in the base and Ml are dominated by endogenous responses to non-policy shocks.

A cash-in-advance model with sequential markets is constructed, where unanticipated monetary injections are nonneutral and can potentially produce large liquidity effects. However, if the monetary authority adheres to an optimal money rule, money should not respond to unanticipated shocks, so that a Friedman rule is suboptimal and the monetary authority does not exploit the liquidity effect. Quantitatively, the model can generate variability in money and nominal interest rates close to what is observed, and can produce data with no obvious evidence of the existence of liquidity effects.